Method for sealing an anode button to a glass cathode ray tube funnel



Nov. 18. 1969 w. E. WILBURN 3,479,169

METHOD FOR SEALING AN ANODE BUTTON To A GLASS CATHODE RAY TUBE FUNNEL Filed June 20, 1966 2 Sheets-Sheet 1 FIG I FIG. C5

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METHOD FOR SEALING AN ANODE BUTTON TO A GLASS CATHODE RAY TUBE FUNNEL Filed June 20, 1966 2 Sheets-Sheet 2 A I INVENTOR.

K l8 WARREN E. lA/ILBURN H BY 7mm 1 PFIT'ORNEVS United States Patent 3,479,169 METHOD FOR SEALING AN ANODE BUTTON TO A GLASS CATHODE RAY TUBE FUNNEL Warren Ernst Wilburn, 474 Rumsey Road, Columbus, Ohio 43207 Filed June 20, 1966, Ser. No. 558,835 Int. Cl. C03c 29/00 U.S. C]. 65-59 3 Claims ABSTRACT OF THE DISCLOSURE This invention relates specifically to sealing a metallic anode button into an aperture in the sidewall of the body portion of an essentially all-glass cathode-ray tube envelope, by axially elevating said button and its closely surrounding glass on a support member moving in a direction towards and in axial alignment with said aperture. The method provides an improved seal with less re-entrancy to provide a durable glass-to-metal seal in the sidewall of an evacuated glass envelope.

The present invention relates to a method of sealing a metallic element in the sidewall of a glass article and more specifically to sealing a metallic contact member through which electrical current is passed between opposing surfaces of the glass envelope sidewall of a cathode-ray tube.

In the manufacture of cathode-ray tubes having essentially all-glass envelopes of the type now generally used in the television industry, the tube envelope is usually provided with a conductive coating on its inner surface which is connected to an electrical circuit disposed exteriorly of the tube envelope through an electricallyconductive element commonly referred to as an anode button which is sealed into the tube sidewall. Sealing of the button is usually performed by lowering the button into an aperture formed in the glass sidewall and applying heat to the button and surrounding glass until the button is wetted by the softened glass when it attains a heat-softened condition. Application of the heat during the sealing operation must be carefully controlled and it is normal for the glass immediately surrounding the button to sag into an undesirable condition during formation of a suitable glass-to-metal fusion-type seal.

In prior practice, sealing in and repositioning of an anode button in the funnel sidewall has been accomplished by simply pushing the anode button and surrounding heat-softened glass upwardly into the final position immediately following the controlled heating, the button being retained in final position until the surrounding glass sets up. Thus, further sagging is avoided. Where the pushing upwardly is effected automatically, such as on a button sealing machine at rapid rates of manufacture, simply pushing the button and surrounding glass upwardly into final position and holding the same in desired relation results in a process delay which limits the speed of manufacturing operations. Also unless the button-glass heating and subsequent repositioning are very precisely controlled, some re-entrancy can occur at the glass-metal interface which is extremely detrimental in the manufacture of electron discharge tube devices.

Several prior art methods and apparatus for sealing an anode button in the wall area of a tube funnel are disclosed in U.S. Patent Nos. 2,637,942 and 2,637,943 to "ice Hinkley and Painter, respectively. Both of these patents disclose so-called button sealing machines which are adapted to moving a funnel on a rotary table through a series of Working stations to effect fusion-sealing of the button in an intermediate area of the funnel sidewall. The Painter patent discloses a method of repositioning the anode button into final position by applying a vacuum bell over the button and surrounding glass to elfect upward movement thereof into final position by reduced pressure thereover. Such method has not been particularly effective in eliminating re-entrancy conditions which can and do occur at the glass-metal interface and which cannot be tolerated even in small numbers in the manufacture of high-performance cathode-ray tube envelopes.

Accordingly, it is an object of the present invention to provide a method of sealing a metallic element in an aperture in a glass article sidewall by a repositioning technique which is adaptable to automatic accomplishment at a rapid rate without a re-entrancy condition becoming existent at or adjacent the glass-metal interface.

Another object of this invention is to provide a method of repositioning a metallic anode button which is fusionsealed in an aperture in the sidewall of a hollow glass article during the interval when the glass surrounding the button remains workable following its fusion to the button.

Another object of the present invention is to provide a method of fusion-sealing a hollow metallic anode button in a sidewall aperture of a hollow glass funnel member of a television picture tube envelope by controlled cooling of the glass-metal interface immediately following heating to provide a strengthened contour thereat The specific nature of this invention, as well as other objects and advantages thereof will become apparent to those skilled in the art from the following detailed description taken in conjunction with the annexed sheets of drawings on which, by way of preferred example only, is illustrated the preferred embodiment of the invention. On the accompanying drawings: FIG. 1 is an enlarged vertical sectional view of one portion of the glass envelope of a cathode-ray picture tube.

FIG. 2 is a view similar to FIG. 1 showingthe step of heating a localized area of the envelope sidewall.

FIG. 3 is a view similar to FIG. 2 showing a punch and die assembly for forming an aperture in the heated sidewall. p

FIG. 4 is a view similar to FIG. 3 showing the aper ture formed in the sidewall.

FIG. 5 is a view similar to FIG. 4 showing a metallic anode button deposited in the aperture with further heating. v

FIG. 6 shows further heating of the anode button and surrounding glass resulting in softening of the latter and sagging of the button area.

FIG. 7 is a view similar to FIG. 6 showing localized cooling of the anode button and closely surrounding glass sidewall in the sagged position.

FIG. 8 is a view similar to FIG. 7 showing the button and surrounding sidewall moved into final position with continued cooling.

FIG. 9 is a perspective view of a completed funnel member showing the anode button sealed in place.

The present invention, as described hereinbelow, is specifically applicable to the manufacture of the funnel member of a television cathode-ray picture tube; however, it will be apparent to those skilled in the art that the invention is; equally applicable to the manufacture of many different types of glass envelopes to be utilized in vacuumized condition, particularly cathode-ray image tubes or other electron discharge devices.

Referring to the drawings in detail, and particularly to FIG. 1, a sidewall 10 of the tube envelope having substantially uniform wall thickness, such as in the medial region of the funnel member 11, is taken for mounting an anode button therein. Normally, a pair of juxtaposed burners 12 are brought into close proximity with opposing sides of the glass sidewall disposed in a horizontal plane to facilitate heating a selected localized area 10a into heat-softened condition. A common type of television glass composition having a softening point temperature of about 1210 F. is heated to an elevated temperature substantially thereabove. Burners 12 may be continuously rotated to deliver a uniform pattern of needle flames in the direction of the opposing glass surfaces for uniform heating.

After the localized area is fully heat-softened throughout its cross-sectional extent to an elevated temperature above its softening point temperature, a punch-and-die assembly is brought into close proximity with the sidewall with its several elements located in cooperative alignment. The punch 13 is then operated to force a small slug of glass from the sidewall through the cooperating die 14 to form an aperture 10b in the softened sidewall area 10a as shown in FIG. 4. The glass surrounding the aperture is then further heated such as by another pair of juxtaposed burners 15 as shown in FIG. 5.

Subsequent to bringing the burners into proximity with aperture 10b for such further heating, an anode button 16 preferably having a frusto-conical shape is forcefully positioned in the aperture such that its frusto-conical side surfaces 16a contact and engage side surfaces of the aperture 10b. Button 16 is usually comprised of an ironchromium-nickel alloy such as Sylvania No. 4 alloy having a thermal expansion coeflicient complemental to the glass and preoxidized surfaces to facilitate glass-to-metal sealing. The button and surrounding glass are both further heated to permit wetting of the button side surfaces by the surrounding glass so that a durable glass-to-metal interface is formed. Such interface is capable of being formed whether the button 14 is preoxidized to facilitate glass-to-metal sealing or preglazed such as by a sealing glass over its side surfaces for such sealing.

As shown in FIG. 6, the button 16 and surrounding glass are further heated to obtain a thermal bond between the glass and metal surfaces. Such further heating results in downward sagging of the button and surrounding glass into a concavo-convex contour at the softened region 100 due to gravitational effects.

Immediately following such further heating to develop a durable hermetic joint between the glass and metal whereby the glass wets the metal and forms a thermal bond with the oxide surface layer, button 16 and the surrounding glass are cooled by a pair of juxtaposed coolant gas outlets 17 which cooling is continued for a sufficient period to set up the glass immediately surrounding the glass-to-metal interface while the button is in sagged position. Pressurized air is a preferred coolant for the purpose and is directed coaxially from both sides in alignment with the button. Such localized cooling is concentrated on the button and closely surrounding glass only to obtain some degree of rigidity of the glassfilleted around the button. The pressurized air is delivered from opposing sides preferably at balanced rates and pressures to prevent any deformation of the heat-softened sidewall due to a blowing action. The button normally being comprised of a hollow cup-shaped thin metal member cools much more rapidly than the surrounding glass. The button is cooled from a temperature of about 2200 F. to about 1100 F. within several seconds during the coolinginterval, and preferably within about one second.

Following such cooling with the button in sagged position, the button and surrounding glass are then moved upwardly into final desired location by a push-up pedestal 18 having a slight central recess complemental to the button bottom. During such'push-up and retention period the upper surface of the button is further cooled by a stream 19a of cooling gas delivered onto the button by coolant outlet 19 to obtain more rapid set up-of the sidewall glass.

Thus, the glass 710d immediately surroundingt e button side surfaces has a desirable filleted contour with no re-entrancy angles on the interior surface which condition is to be avoided in high-quality envelopes. The forced cooling at the indicated central area while in sagged form results in a generally convex exterior contour of the glass surface closely surrounding the button when elevated to desired elevational location in the sidewall. The interior surface of the glass is preferably flat over a relatively broad area surrounding the button, its degree of planeness being measured by a reflectometer to determine its surface contour. The glass closely adjacent the button is not contacted by the push-up pedestal upper surface. The cooled glass remains in filleted condition around the button side surfaces and no re-entrancy thereat is created by the repositioning. Filleting of the glass at both the upper and lower areas of the button side surfaces is reproducibly controlled to form a durable hermetic seal devoid of fracture sources. Proper filleting is necessary to obtain the improved seal and the fillets are not disturbed by the subsequent moving of the button into final position.

Television picture tube funnels made in accordance with this invention have shown much improved seal contours and virtually eliminated sources of fracture originating at the anode button area in both black-andwhite color tubes. The prescribed method permits faster processing of funnels during their manufacture with considerably improved results.

What is claimed:

1. In the method of repositioning a hollow metallic anode button which has been fusion-sealed by heating in an aperture in the sidewall of a hollow glass funnel member of a cathode-ray tube envelope during the interval when the glass in the peripheral region closely surrounding said anode button and in the outlying peripheral vicinity of said anode button remains above its softening point temperature and sufficiently workable following its fusion to the button to gravitationally sag under its own Weight, said fusion resulting in downward displacement of said button and surrounding workable glass from a de-' sired position with respect to the unsoftened sidewall portion, the improvement in said method comprising the steps of locally cooling that portion of said sagging glass in the peripheral region closely surrounding said anode button at a faster rate of cooling than the remaining portion of said sagging glass in the outlying peripheral vicinity of said anode button, thereby dilferentially reducing the workability of different portion of said sagging glass, axially elevating said button and that portion of said sagging glass in the peripheral region closely sur-' rounding said anode button on a support member moving in a direction towards and in axial alignment with said aperture and thereby elevating said anode button into alignment in said aperture and causing oppositely disposed top and bottom surfaces of the said anode button to draw said differentially cooled anode button.

glass upwardly therewith and into a shape defining 7 References Cited a filleted non-reentrant seal contour extending around i the periphery of said anode button. 5 UNITED STATES PATENTS 2. In the method in accordance with claim 1, includ- 2 637 943 5/1953 p i 5 54 ing the improvement wherein the step of differential cool- 3 107757 10/.1963 Breaoner 5 59 ing of the sagging glass is continued for a suflicient time 3 142 86 3/1964 Bronson et 1 5 59 to establish a nearly set-up condition of only the glass in the peripheral region closely surrounding the anode 10 s LEON BASHORE, p i Examiner button.

3. In the method in accordance with claim 2, including FREEDMAN Asslstant Exammer the improvement wherein the step of US. Cl. X.R.

difierential cooling is carried out by simultaneously 6549, 54,154

applying streams of pressurized cooling gas locally to 15 

